Semiconductor devices, especially power semiconductor devices such as power semiconductor switches often include a temperature measurement functionality for detecting faulty or undesired mode of operations during which undesirably high temperatures may occur. Such faulty or undesired mode of operations may be, inter alia, an over-load, or a short circuit.
Power semiconductor switches capable of detecting over-temperature, over-load, short-circuits, etc., are often referred to as “smart power switches.” In known applications temperature is often measured at two positions, namely one temperature sensor measures the temperature in or close to the active area of the semiconductor device (e.g., of the DMOS switch) and another sensor measures the temperature in or close to the coldest area of the chip. The difference between these two temperature measures may be used to assess the state of the semiconductor device. That is, if the temperature difference exceeds a predefined threshold value or if one temperature measure exceeds a maximum allowable temperature, then the semiconductor device is powered down in order to avoid damage to the device.
In known applications the above mentioned thresholds are predefined constants. The semiconductor device is powered down, for example, when the measured temperature difference exceeds a threshold of 60 Kelvin. However, following such an approach it may be difficult to distinguish a faulty mode of operation (such as a short circuit) from a temperature rise due to ordinary operation with in a sufficiently short period of time. This may be particularly the case when operating at high (battery) supply voltages, that is above about 12 to 15 volts.
Thus there is a need for a thermal fault detection within semiconductor devices that allow for a fast detection of faulty operating states which lead to an undesired rise of temperature.